The present invention relates generally to belt conveyors, and more particularly to a conveyor belt cleaning apparatus for use with such conveyors.
Belt conveyors are used in a variety of applications for the transportation of particulate or granular material, such as coal, grain, ore, minerals, and the like.
One problem commonly encountered with belt conveyors is the tendency for particulate material to adhere to the carrying surface of the conveyor belt. This problem is particularly significant in applications such as underground mining operations and coal transportation, where the material moving on the belt must continually be sprayed with water to suppress dust. The water mixes with the fine particulate component of the coal or other material to form a slurry which is particularly prone to sticking to the surface of the belt. This phenomenon reduces the transportation efficiency, and increases the running and maintenance costs of the conveyor.
In an attempt to ameliorate these problems, various conveyor belt cleaners in the form of scraping devices have been developed to scrape residual debris from the surface of the belt. These are normally positioned on the underside of the conveyor, at or near the head pulley and just past the intended discharge point, such that the lower run of the belt on its return loop is substantially clean.
However, known scraping devices have several inherent disadvantages. The most significant of these relates to the need for the scrapers to accommodate surface irregularities in the belt. Such irregularities most commonly take the form of belt fasteners. which are typically formed from steel and protrude beyond the surface of the belt. These fasteners can cause hardened scraping blades to break, chip or shatter, leading to reduced scraping efficiency and downtime whilst repair operations take place. This can also cause premature failure of the belt fasteners.
In an attempt to avoid these problems, some scraping blades have been formed from relatively soft materials such as polyurethane, polypropylene and other plastics. Whilst being better able to accommodate surface irregularities in the belt without breakage, such blades are prone to rapid abrasive wear, and hence require frequent replacement. This is costly, and again often results in undesirable downtime.
A further problem with known scraping devices relates to the need for each of several-scraping blades to be individually adjusted to the correct position relative to the belt, and relative to the adjacent blades. This set-up procedure is time consuming, labour intensive and expensive. Moreover, frequent recalibration is normally required in order to accommodate wear of the scraping blades.
It is an object of the present invention to provide a belt scraping assembly which overcomes or substantially ameliorates at least some of these disadvantages of the prior art.
Accordingly, a first aspect of the present invention provides a conveyor belt cleaning apparatus for a belt conveyor, the cleaning apparatus comprising:
a shaft,
a pair of mounting assemblies for mounting the shaft to a frame of the belt conveyor,
the shaft being rotatably mounted within the mounting assemblies,
a first arm and a second arm for supporting a scraping blade, the first and second arms independently mounted on the shaft and independently rotatable about the axis of the shaft, the mountings of the first and second arms adapted to bias the respective arms towards the conveyor belt surface,
the apparatus further including a third arm mounted on the shaft and located intermediate the first and second arms for supporting the scraping blade,
such that rotation of the arms about the axis of the shaft results in positional adjustments of the scraping blade with respect to the conveyor belt surface, the arms being pivotably connected to the scraping blade to provide relatively uniform contact pressure between the blade and the conveyor belt surface across the width of the blade.
In use the scraping blade is maintained in a plane substantially perpendicular to the plane of the conveyor belt surface.
Preferably, when mounted to the frame of the belt conveyor the axis of the shaft is substantially transverse to the direction of movement of the conveyor belt.
Preferably, the mountings of the first and second arms each include a resilient element configured to urge the scraping blade into operative scraping engagement with the conveyor belt surface. In one preferred embodiment the resilient element comprises a torsion spring. In another preferred embodiment the resilient element is formed from a resiliently deformable material.
Preferably, the mountings are adjustable so as to produce the desired contact pressure between the scraping blade and the conveyor belt surface.
In one preferred embodiment, the mountings of the first and second arms each include a pair of collars comprising a first collar which is rotatably mounted on the shaft and to which a respective arm is connected and a second collar adapted to be locked in position on the shaft, a torsion spring being interposed between the first and second collars with free ends of the torsion spring engaging with the first and second collars, wherein by rotatably adjusting the relative position of the first and second collars on the shaft it is possible to adjust the spring tension in the torsion spring and the biasing torque imposed on the arms connected to each end of the scraping blade.
Preferably, each mounting assembly further includes a locking collar through which the shaft passes and which is locked in position on the shaft, a mounting block, and a torsion spring interposed between the locking collar and the mounting block, with one free end of the torsion spring being engaged in the locking collar and a second free end being engaged in the mounting block so as to provide a torque on the shaft.
Preferably, the third arm comprises a first link and a second link which are pivotably connected together at a hinge point, the first link being connected to the shaft and the second link being connected to the scraping blade. Preferably, the second link is adjustable in length by means of a threaded shaft and nut arrangement.
Preferably, the conveyor belt cleaning apparatus according to the present invention is adapted to be positioned on the underside of the conveyor belt so as to clean the carrying surface of the conveyor belt as it returns from its discharge point.
Advantageously, the present invention provides a conveyor belt cleaning apparatus for positioning a scraping blade against the surface of a conveyor belt and which is designed to maintain a relatively uniform blade pressure across substantially the full width of the blade, whilst maintaining the blade in a plane substantially perpendicular to the plane of the conveyor belt surface.
The present invention has particular application with a curved scraping blade, although the invention may be adapted for use with a straight (also known as xe2x80x9cinlinexe2x80x9d) scraping blade. Currently, belt cleaners which employ a curved blade use an adjustment mechanism which produces an arced motion so as to bring the cleaner blade into contact with the conveyor belt. This results in a non-uniform pressure across the width of the blade, with greater pressure being applied around the mid point of the cleaner blade.
Unless the context clearly requires otherwise, throughout the description and the claims, the words xe2x80x98comprisexe2x80x99, xe2x80x98comprisingxe2x80x99, and the like are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of xe2x80x9cincluding, but not limited toxe2x80x9d.